(CNN) — Sen. Hillary Clinton’s lead over Sen. Barack Obama in the crucial primary state of Pennsylvania has dwindled to 4 points, a CNN average of recent polls calculated Thursday shows.

The New York senator now holds a 4 point advantage over her rival for the Democratic presidential nomination, 46 to 42 percent. Twelve percent of likely Democratic voters there remain unsure.

Recent CNN “poll of polls” suggest the race in Pennsylvania is tightening before the state’s April 22 primary. A poll of polls calculated two days ago showed Clinton with a 6 point lead in Pennsylvania, and a poll of polls last Friday showed her on top by 11 points.

“Obama is outspending Clinton by better than two to one on television ads in Pennsylvania,” said Alan Silverleib, CNN’s senior political researcher. “Combine that with Clinton’s recent misstatement over her 1996 trip to Bosnia and the escalating chorus of voices calling on her to withdraw from the race, and you get a much tighter contest.”

Thursday’s poll of polls included recent surveys from Time Magazine, American Research Group, and Quinnipiac University.